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Re: [TLS] Which SHA function should I use for CertificateVerify of a rsa_pkcs1_sha1 certificate?

Ilari Liusvaara <ilariliusvaara@welho.com> Fri, 14 October 2016 15:43 UTC

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Date: Fri, 14 Oct 2016 18:43:27 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Hubert Kario <hkario@redhat.com>
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Subject: Re: [TLS] Which SHA function should I use for CertificateVerify of a rsa_pkcs1_sha1 certificate?
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On Fri, Oct 14, 2016 at 05:15:48PM +0200, Hubert Kario wrote:
> On Friday, 14 October 2016 14:34:49 CEST Kazuho Oku wrote:
> > Considering that, to me it seems preferable if the draft stated that
> > both PKCS1 and SHA1 are obsoleted, and are allowed to be only used in
> > certificates. Or is there any need to handle PKCS1 and SHA1
> > differently in protocol implementations?
> 
> there isn't, the only case is when you also implement TLSv1.2
> 
> Pure TLSv1.3 implementation shouldn't ever generate messages or try to verify 
> messages signed with SHA-1 (or MD5 for that matter)

Unfortunately while one sees less and less use of SHA-1 as certificates
expire, there still is use of SHA-1 in OCSP. The only place where my
TLS library uses SHA-1 is with OCSP.


-Ilari

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